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Project ZXR250A - The Wasp.

Discussion in 'Your 250cc Projects' started by Murdo, Aug 14, 2018.

  1. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    My comment - I have refitted barrels on both the FZR and ZXR without using special tools or hose clamps to compress the rings. Both have chamfers if the bore is standard. It's a fiddle job but can be done by hand with patience and proper technique.
     
  2. jmw76

    jmw76 Well-Known Member Premium Member

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    Patience????? I don't think I have that tool.
     
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  3. jmw76

    jmw76 Well-Known Member Premium Member

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    Try doing it on a Suzuki GSXR 1100 with an 81mm bore and cylinder studs and central timing chain to work around.
     
  4. Andych

    Andych Senior Member Premium Member

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    Typical method for Honda 4 SOHC engines is to have 2 bocks of alloy or timber to support 2 pistons slightly higher then the others and then slowly work the rings in as the taper / chamfer is more of a guide than a replacement for a ring compressor.
    Ring position is fairly standard practice. No ring ends overlapping and positioned away from wrist pins.
    I have seen people line all the ring gaps and wonder why they destroyed a set of rings during run in.

    I am sure @Murdo has his tried and true method of assembly that will work just fine.


    Sent from my iPhone using Tapatalk Pro
     
  5. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Chamfer is pretty good on the Kwaka barrels. You can't get the standard tool (57001-1312) for love nor money, so I've always done it with the 'free-style' method. I have a ring compressor for small diameter pistons, but I've never used it. I'm keen to hear how Murdo and Matt did it.
     
  6. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    I was actually referring to the oil ring gaps pointing towards the front and slightly spread over 60 to 80 degree from each other. People keep telling me ring gaps need to be set at 120 degrees from the nearest ring's gap. That might be true, but that's not how Kawasaki wants you to layout your rings on a ZXR250.
     
  7. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Did the rings as per the book and made a piston holder from a 10x3mm flat bar. Took a lot of fiddling but we got them in. Spent all morning taking off the radiator and exhaust to get the starter out and rebuilt. (Be warned, there are four springs behind the brushes that fly in four different directions when you take the armature out.) Starter back in and cranking nicely. Exhaust and rad back on and fired for short run (no water in yet).
    xx 001.jpg
     
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    Last edited: Dec 30, 2020
  8. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Excellent. I'm pretty good at getting the barrels back on free-style, but I'd be happier if I had a bespoke tool for the job. I'm looking forward to getting up to you in March, if the 'Weeks of Speed' event goes ahead and we're still allowed to cross borders.

    I've rebuilt a few ZXR starter motors. They mostly seem to oil up or become notchy, so a good clean, re-grease the bearing, check everything is within tolerance and away we go. How much fun is it trying to put it back together with four springs and magnetism working against you?
     
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  9. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    My Bike:
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    Time for an update.
    The SU carb would not lift the slide when running. I removed the oil from the damper, then took the spring out and still it would not lift without finger help. I bought a 34mm OKO flat slide and made a new mount to fit it. This has just been the biggest headache I have ever come across when trying to tune it.
    Matt on mower 012.jpg Matt on mower 009.jpg
    I have jetted it from 100 (too lean to run) to 200 (floods on opening the throttle) on the mains, from 25 to 50 on pilots, needle up and down on all settings, so yesterday I made some different needles and got it better but is still not right.
    Started with some 3mm brass welding wire and centre drilled it.
    XT600 & MEC 2 035.jpg
    Then turned the five adjustment grooves for the circlip and trimmed down to the outer diameter over the full length. Made two to make different profiles.
    XT600 & MEC 2 037.jpg
    XT600 & MEC 2 045.jpg
    New ones turned out quite nice but still did not fix the tuning although better.
    XT600 & MEC 2 047.jpg
     
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  10. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    And it appears to be a powerjet version (for 2 strokes), or did you blank that off?
     
  11. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    It actually has a blanking plug in it, ie no jet.
     
  12. Tigger996

    Tigger996 Well-Known Member

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    Yamaha-Fzr250-3LN-EXUP 1989. Yamaha FZR400 road and Yamaha FZR400 race, Yamaha FZR400 with FZR600R engine, Ducati 998S & 996 & 900SS & ST4. Dresda Triton. Suzuki T500 road & T500 race. RS125 with Rotax 257 engine. and a couple of Ossa trials bikes in bits and a Sachs rolling chassis
    I have never used forced induction on my bikes, but LOTS of friends who also sprint/drag do. They say never use flat slides on forced induction as the pressure differential either side of the slide will cause it to lock up. The SU is the best choice. If you need advice do a facebook search for "national sprint association" "British Drag Bike History" the members will be able to advise.
     
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